JPS585733B2 - Shiborishigokikanyouseikeikougu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a forming tool for forming a cup-shaped container by drawing and ironing, and in particular, a forming tool for drawing and ironing cans in which the cup-shaped container after forming can be easily removed from the tool. Regarding forming tools.

Generally, in forming cup-shaped containers made of aluminum, after drawing and ironing, the cup-shaped container is removed from the tool.During the return stroke of the tool, a stripper of a simple structure is attached to the opening side end surface of the cup-shaped container. This can be done relatively easily by making contact with the tool and moving it relative to the tool.

However, in forming tin cup-shaped containers, the stripper for forming aluminum cup containers often causes buckling of the open end of the container during stripping.

That is, in order to save material, the body of a cup-shaped container made of tin is made several times thinner than that of aluminum, and cannot withstand the force of tearing the container out.

Such buckling must be eliminated because the buckling becomes a hindrance in the subsequent trimming process.

Conventionally, as a means to solve this problem, a member that passes through the center of the punch is provided so as to be able to protrude toward the tip of the punch.
There is a so-called internal knock-out method (Japanese Patent Publication No. 45-9837) in which the member is extracted by protruding it after ironing, but the mechanism is complicated because the member needs to be driven from the outside, and it requires high speeds. During operation, the movement of the machine body and the movement of the internal knockout mechanism tend to be out of harmony, and the cup-shaped container may not be able to be pulled out of the punch.

Another method is to provide a taper in the punch body so that the diameter gradually increases from the tip, and the taper of the bracket is larger than the taper of the corresponding part of the cup-shaped container (Japanese Patent Laid-Open No. 4
No. 7-33868), but it had the drawback that the wall thickness at the tip of the molded container became large, resulting in wasted material costs.

The present invention has been made to solve the above-mentioned conventional drawbacks, and the punch is formed of a punch center and a punch sleeve that is fitted with a taper on the outer periphery of the punch center. The diameter of the sleeve is expanded by the taper and returned to its original position during extraction, thereby forming a gap between the formed container and the punch, allowing the container to be extracted from the punch under a small load without any damage. The purpose of the present invention is to provide a forming tool for drawn and ironed cans that can minimize the material used for containers.

The present invention will be described below with reference to embodiments shown in the drawings.

The punch 1 of the forming tool for drawn and ironed cans according to the present invention includes a punch center 3 that is directly connected to a ram 2 of a machine body (whole illustration is omitted), and a punch center 3 that is fitted onto the outer periphery of the punch center 3 to fit inside the container to be formed. A punch sleeve 4 having an outer shape similar to the punch sleeve 4 is provided.

Both are made of materials such as tool steel and cemented carbide.

The punch center 3 has a stepped portion 5 whose outer diameter becomes smaller at its upper portion, and further has a tapered body portion 6 whose outer diameter gradually decreases from the stepped portion 5 toward the tip.

The punch sleeve 4 also has a tapered inner peripheral surface 7 whose inner diameter gradually decreases from the upper end to the lower end with the same taper as the tapered trunk 6. The punch center 3 is fitted into the punch center 3 so as to surround the punch center 3 .

When the punch sleeve 4 is fitted to the punch center 3, the punch sleeve 4 has an inner step 8 located at the same position as the tip of the punch center 3, and a tip peripheral wall that protrudes further forward from here and forms a recess 9 inside the tip. 10.

A stopper 11 is screwed into the recess 9 at the tip of the punch center 3, thereby regulating the punch sleeve 4 so that its inner step 8 is at the same height as the tip of the punch center 3. be done.

Further, the length of the punch sleeve 4 is such that the upper end is located below the step 5 of the punch center 3 by a gap 12 when the inner step 8 is in contact with the stopper 11.

Reference numeral 13 in the figure is an air vent hole provided through the center of the punch center 3 and stopper 11 in order to smoothly attach and detach the workpiece W, and 14 is an air vent hole that supplies lubricating oil to the tapered body 6 and the tapered inner circumferential surface 7. 15 and 16 are O-rings for preventing lubricating oil from leaking and adhering to the workpiece W, and 17 is an oil groove provided on the outer periphery of the tapered body.

Note that the punch sleeve 4 in this embodiment has a slightly larger outer diameter at a length of about 100 mm from the lower end than at the upper part; This is to give the cup-shaped container the minimum thickness that can be processed without causing wrinkles or cracks during processing.

The tapered body portion 6 and the tapered inner circumferential surface 7 are tapered at a relatively small angle of 1 degree to 5 degrees.

That is, when the taper is less than 1 degree, the punch sleeve 4 can be sufficiently expanded by fitting with the punch center 3, but it may not return to its original position when being pulled out.

The wear is related to the surface conditions of the tapered body 6 and the tapered inner peripheral surface 7 and the viscosity of the lubricating oil used.

When the taper was 5 degrees or more, the punch sleeve could not expand sufficiently to be effective when extracting the cup-shaped container from the punch sleeve 4.

Next, the operation of the above embodiment will be explained with reference to FIGS. 2 and 13.

Punch center 3 and punch sleeve 4 by ram 1
The workpiece W attached to the punch sleeve 4
is drawn and ironed using die D.

At this time, the punch sleeve 4 receives an upward force from the die D via the workpiece W, and as a reaction, a wedge action occurs in the taper of the taper body 6 and the taper inner peripheral surface 7, and its diameter (outer diameter and inner diameter) are elastically enlarged and the upper end portion is slid upward until it collides with the step portion 5.

(See FIG. 2, the amount of diameter expansion is determined by the value of the taper and gap 12.) This behavior is shown in FIG.

When the substantially solid punch center 3 is lowered, an upward force is applied to the punch sleeve 4 as described above.
The punch center 3 is pushed into the punch sleeve 4.

Due to this relative movement, the thin punch sleeve 4 is expanded in the radial direction as shown by the chain line A in the figure.

Of course, this expansion takes place within the elastic limits of the punch sleeve 4.

Therefore, if the punch center 3 is pulled out from the punch sleeve 4, it can return to its original diameter depending on the amount of expansion.

For this reason, it is necessary to keep the amount of expansion within a range in which the punch sleeve 4 can be elastically deformed.

Specifically, the outer diameter of the tip of the punch center 3 is 42φ and the taper angle is 2 degrees using tool steel, and the large diameter portion extending approximately 100 mm from the lower end of the punch sleeve 4 is 65.37 mm.
When the diameter of the upper small diameter portion is 65.25 φ and a load of about 2 tnn required for forming is applied, the radius expansion amount of the punch sleeve 4 is about 20 to 30 μm.

Here, the stress generated in the sleeve 4 when the forming load is applied is α=30 to 35 kg/mm 2 , which is within the elastic limit of tool steel (60 to 70 kg/mm 2 or more).

Note that the amount of expansion in cemented carbide is about half that of tool steel, but since it has a high elastic limit, it is also possible to increase the forming load, and the same effect can be obtained.

After the drawing and ironing process by the ironing die D is completed, the ram 1 enters a return stroke, and the punch center 3, punch sleeve 4, and workpiece W are raised.

During this upward movement, the workpiece W collides with the stripper S that has been projected in advance so as to come into contact with the upper end of the workpiece W, and is prevented from moving upward, causing the workpiece W to move relative to the punch center 3. A downward force is applied to the workpiece W.

Therefore, the punch sleeve 4, which is in a pressure-fitted state with the workpiece W, is also slid downward relative to the punch center 3 by applying a downward force, and as shown in FIG. It is moved to a position where the stepped portion 8 is brought into contact with and a gap 12 is formed at the upper end.

At this time, the punch sleeve 4 is moved toward the small diameter portion of the tapered body 6 of the punch center 3, and its inner and outer diameters are elastically contracted and returned to their original state.

When the container is removed, when the upper end of the container comes into contact with the stripper S, a gap or slack is created between the inner diameter of the container and the outer diameter of the punch sleeve 4, and the punch center 3 and punch sleeve 4 further rise from the above state. Therefore, even if a relative force is generated between the punch sleeve 4 and the workpiece W, the force is relatively small, and the workpiece W is smoothly pulled out from the punch sleeve 4.

Here, in this embodiment, the punch sleeve 4 has a shape having a large diameter part corresponding to the can body and a small diameter part corresponding to the container rim.
mm), so the portion corresponding to the mouth edge, which has a small diameter, hardly affects the extraction force.

Moreover, since the entire punch sleeve 4 uniformly expands and contracts in the radial direction, the effect of reducing the extraction force is significantly greater than that of conventional stepped punches that cannot expand and contract.

In the above embodiment, the outer diameter of the upper part of the punch sleeve 4 is smaller than that of the lower part, but they may have exactly the same diameter.

As described above, the present invention provides a forming tool for drawn and ironed cans, which includes a punch center having a tapered body that becomes smaller in diameter toward the tip of the punch, and a tapered inner circumferential surface that fits into the tapered body of the punch center. During drawing, the diameter of the punch sleeve expands due to the wedge action of the tapered part, and when the workpiece is removed, the diameter decreases and returns to its original shape. A gap or slack is created between the outer periphery of the punch sleeve and the inner diameter of the workpiece when the workpiece is removed, and the workpiece has the excellent effect of being able to be removed from the punch without any damage under a small load.

According to experiments conducted by the present inventor, the punch center and the punch sleeve were tapered by 1 degree, the gap 12 was made to have an enlarged radius of the punch sleeve of 30 μm, and the outer shape of the punch sleeve was straight, with a roughness Rmax of 2.0 μm. In this case, the extraction force was approximately 1/7 of that of the conventional method.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the drawing and ironing can forming tool according to the present invention, FIGS. 2 and 3 are cross-sectional views showing the operation of the same embodiment, and FIG. 4 is a cross-sectional view of the tool. It is. 3...Punch center, 4...Punch sleeve, 6...Tapered body, 7...Tapered inner peripheral surface, D...Die , W... Workpiece, S... Stripper.

Claims (1)

[Claims] 1. A substantially cylindrical punch center having a tapered body whose outer diameter slightly decreases in the direction of the tip and an air vent hole, and a tapered inner circumferential surface that matches the tapered body of the punch center. A forming tool for a drawn and ironed can, comprising a cylindrical punch sleeve fitted to the outer periphery of the punch center body so as to be slidable within a certain range in the axial direction. 2. In the drawing and ironing can forming tool according to claim 1, the taper angle of the tapered body and the tapered inner peripheral surface is 1 degree to several degrees with respect to the axes of the punch center and punch sleeve. Characteristic forming tool for drawn and ironed cans.